Nearly one year into House Republicans' probe of federal loan guarantees to Solyndra, investigators are still looking for "the proverbial smoking gun," as one lawmaker put it.

"We never said there was corruption," House Energy and Commerce Chairman Fred Upton told Roll Call. "We wanted to get to the bottom of the story. How did the taxpayers end up losing $535 million? Why was it that the taxpayers were put last?"

The Michigan Republican's committee has been investigating whether White House officials improperly pressured the Energy Department to issue a $535 million loan guarantee to Solyndra, the now-bankrupt solar panel company whose offices were raided by the FBI in September.

"We're not done. The investigation's not done. It's been pulling teeth," Upton added.

Rep. Cliff Stearns, the Florida Republican who heads the Energy and Commerce Subcommittee on Oversight and Investigations, offered a more robust opinion about what had been uncovered but conceded investigators did not have all of the pieces.

"Oh, yes," Stearns said when asked if the probe had uncovered evidence of corruption. "There's evidence to show they asked Solyndra to delay people being laid off till after the midterm elections."

He added, "I think we've got the smoke. We need to get access to the White House West Wing to, shall we say, clarify the reasons why this happened."

Documents released show the administration did little when presented with information that Solyndra was a financial risk.

In October 2010, Solyndra executives told the Department of Energy that it was financially teetering and about to lay off workers. The department's chief loan officer, Jonathan Silver, forwarded an email with the news to Ron Klain, who at the time was Vice President Joseph Biden's chief of staff, and Carol Browner, who was then Obama's energy and climate change coordinator.

Emails from associates of George Kaiser, a top political fundraiser whose foundation invested in Solyndra, show the firm then delayed the announcement of those layoffs until Nov. 3 — the day after the midterm elections — "per DOE's request."

Stearns said that would "indicate" the White House told Silver, who has since left DOE, to make that request.

Republicans have asserted that the White House Office of Management and Budget's review of the Energy Department's work on the loan guarantee might have been rushed to accommodate a publicity push.

The Energy Department also later changed the terms of the loan so that investors were first in line to be repaid ahead of taxpayers if the firm failed.

Kaiser met repeatedly with senior White House officials such as Rahm Emanuel, Valerie Jarrett and Pete Rouse in 2009 and 2010.

"OK, I'll admit it. It was pretty intoxicating. Two hours at dinner. They sat me right next to Him," Kaiser recalled in an email about a fundraising dinner he shared with the president.

Throughout the investigation, the White House has held firm that there was no undue influence exercised on behalf of the firm.

"We are entering month 10 of this investigation, and everything disclosed in the 185,000 pages of documents, nine committee staff briefings, five Congressional hearings, emails from Solyndra investors and [a] committee interview with George Kaiser affirms what we said on day one: This was a merit-based decision made by the Department of Energy," Obama spokesman Eric Schultz said.

But some Republicans, including Upton's predecessor as head of the Energy and Commerce panel, Rep. Joe Barton (Texas), say it's more complicated than that.

"We have not yet found the proverbial smoking gun in terms of some political quid pro quo, although we have not yet really interviewed the key people at the White House. If such evidence exists, that's probably where it's going to be," Barton said.

Barton also asserted that even if there was improper politician influence, it was unlikely such a thing would be openly discussed.

"It's the elephant in the room that nobody talks about," Barton said. He added that Kaiser might never have raised Solyndra to White House officials, "but everybody knew who he was and what he had done." Still, innuendo falls outside the boundaries of fact-based evidence.

"I don't think there was criminal intent going into this issue. I think there was naivet&eacute;," Rep. Brian Bilbray (R-Calif.) said.

Bilbray recently defended Energy Secretary Steven Chu at a hearing. "I sense he's fallen on the grenade for somebody else that pulled the pin," he explained.

"The one place I see criminal activity where the line was crossed was with the refinancing," Bilbray said.

"They broke the law on subordination. That's clear. The law clearly states you can't do what they did. Now that's a fact. And it doesn't matter what their deputy general counsel wrote in a memo, they broke that law," Barton said.